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Help with bicycle rig

I have a bicycle that I cannot get to stick to the ground. I think it has something to do with "auto origin" being used in the Raycast Geometry setup, but maybe it's the rig itself. The "driver null" is the one with the actual animation attached to it, but it must be raycast so the front and back wheels can reach the ground. At any rate, I've included a labelled picture so you can see where I've gone wrong.
NOTE-- the surface I have them raycast to and their starting positions are NOT 0,0,0-- if that has anything to do with it.
Any help would be appreciated.

displacing child objects which parent is also displaced is usually a p.i.t.a. Doing it in a longer hierarchy is even worse. The good news is that it's doable! I've modified your scene and attached it. I think this is what you wanted to happen. Basically what I did was to make both "wheel nulls" childs of the "driver null" (instead of one wheel beeing a child of the other, which would add to the node mess )
Then, the problem with raytracing displacement of child objects is that you get the result as world coords, and to translate that to (parent) object space you have to know the position of the parent. Item info node gives you only the keyframed position so you have to trace it's new position also.
The ADD 10m node is just there to ensure you don't start tracing below the ground.

Good luck!

And yeah, I changed the texture on the ground to a plain procedural, because there was an image lacking in your scene. Ground was just pitch black.